1. Field of the Invention
The present invention relates to an apparatus and method of driving a transfer belt. More particularly, the present invention relates to an apparatus and method of driving a transfer belt on a standby mode or a power-saving mode to prevent deformation of the transfer belt.
2. Description of the Related Art
Image forming apparatuses, such as printers and photocopiers, generally include a photoconductive unit having a photosensitive medium on which an image is developed, and a transfer unit which transfers the developed image onto a transfer medium such as paper. The transfer unit has a transfer belt which runs along a continuous track.
FIG. 1 shows an image forming apparatus which employs the transfer unit having the transfer belt as described above. Reference character ‘P’ indicates a paper conveyance path.
As shown in FIG. 1, an image forming apparatus 30 includes a photoconductive unit 10 having a photosensitive medium 11 such as an OPC drum, a laser scanning unit 12, a developing device 13, a transfer unit 20 having a transfer belt 14, a plurality of rollers for moving the transfer belt 14 along a continuous track, and a fusing roller 21 for fusing an image. The plurality of rollers include a first transfer roller 16 which transfers an image onto the transfer belt 14, a second transfer roller 19 which transfers the image onto the transfer medium such as paper, a tension roller 18 which adjusts a tension of the transfer belt 14, a nip roller 17, and a backup supporting roller 15 which idle-rotates in association with the rotation of the second transfer roller 19. All the parts mentioned above are operated in conjunction with one another and perform a series of processes in the following sequential order: electrical charging, laser-scanning, developing, transferring and fusing, to form a desired image.
FIG. 2 is a flowchart showing a method of driving the transfer belt as shown in FIG. 1. The method of driving the transfer belt is described below.
First, the image forming apparatus 30 is in a home mode, in which the image forming apparatus 30 is in a power-on state and is supplied with power, or has finished printing at step S9. During the printing operation, the transfer belt 14 comes into contact with the photosensitive medium 11 and the transferring medium to transfer the image formed on the photosensitive medium 11 to the transferring medium.
It is determined whether a work signal is input in the image forming apparatus 30 at step S10. The presence or absence of the work signal is determined by a controller 31 which is disposed in the image forming apparatus. If a work signal is input, the printing operation starts according to the work signal at step S11.
If the work signal is not input, the controller 31 enters a standby mode to stop the operation of a driving source 32 such as a motor of the image forming apparatus at step S12. At step S13, the controller 31 compares a lapse time ‘ta’ measured from the beginning of the standby mode to a first reference time ‘t1’. If the lapse time ‘ta’ is greater than the first reference time ‘t1’, the controller 31 enters into a power-saving mode at step S14.
The power-saving mode prevents power from being supplied to a high power consumption unit such as a heat lamp for heating the fusing roller, to conserve power when the image forming apparatus is in the standby mode for an extended period of time.
In the conventional image forming apparatus 30, the transfer belt 14 does not rotate when the image forming apparatus 30 enters the standby mode or the power-saving mode after the power supply or the print job. Consequently, in the standby mode or the power-saving mode, the transfer belt 14 maintains contact with the plurality of rollers 15, 16, 17, 18, 19 at the same positions. Subsequently, pressure is applied to the same points. When the standby mode or the power-saving mode lasts long, the pressure to the transfer belt 14 becomes greater.
Also, if the pressure is exerted to the contact points between the transfer belt 14 and the plurality of rollers 15, 16, 17, 18, 19 while the image forming apparatus 30 remains at a high temperature such as shortly after the standby mode or the power-saving mode, traces of the plurality of rollers 15, 16, 17, 18, 19 remain on the transfer belt 14 in a stripe pattern, and therefore cause a deformation of the transfer belt 14. Such a deformation is particularly severe in the area where the transfer belt 14 contacts the tension roller 18 and the first transfer roller 16.
The problem worsens as the deformation of the transfer belt causes image blurring during the transfer of the image, and if this happens, a user cannot obtain a clear image.